I. Field of the Invention
The present invention relates to a device for supplying hydrogen to a fuel cell used in particular for electric propulsion of a motor vehicle, and it relates more particularly to fuel cells of the PEFC type (polymer electrolyte fuel cell).
II. Description of Related Art
The fuel cell increasingly appears to be the most appropriate and most efficient energy converter for converting chemical energy into energy that can be directly used in electrical and thermal form.
Its operating principle is simple: it comprises controlled electrochemical combustion of hydrogen and oxygen with simultaneous production of electricity, water and heat according to the following chemical reaction: H2+½O2→H2O. This reaction takes place in a structure composed substantially of two electrodes, the anode and cathode, separated by an electrolyte: it is the reverse reaction of the electrolysis of water.
Since the fuel supplying the anode for the electrochemical reaction is hydrogen, two solutions are available to the user. A first solution is to store the hydrogen close to the cell and to consume it as needed. Today, however, this poses numerous problems such as the method for production of the hydrogen, the economical and environmental cost thereof, the manner of storage thereof and even the safety of use thereof. A second solution is to produce the hydrogen from a hydrogen-containing fuel, such as an alcohol or a hydrocarbon. The system with which fuel can be transformed to hydrogen is known as a hydrogen processor. It traditionally uses a plurality of process steps, which may be chemical or physical. The processor is composed mainly of a first reforming stage, in which the fuel is converted to a mixture of H2, CO2, CO, N2 and H2O. This stage is directly followed by purification aimed at reducing the carbon monoxide concentration, in view of its highly toxic nature for humans and for the fuel cell.
These hydrogen processors, however, have the disadvantage that they are cumbersome and expensive.